JP5871142B2 - Communication device and encryption key generation method in encryption key sharing system - Google Patents

Description

  The present invention relates to a system for generating an encryption key based on random number information once shared, such as a quantum key distribution technique, and more particularly to a communication device and an encryption key generation method thereof.

  The Internet, which continues to grow at a rapid pace, is convenient, but has great concerns about its security, and the need for cryptography is increasing to keep communications secret. Currently used encryption methods are classified into secret key encryption such as DES (Data Encryption Standard) and Triple DES, and public key encryption such as RSA (Rivest Shamir Adleman) and elliptic curve encryption. However, these are encryption communication methods that guarantee the security based on “computational complexity”, and always have a risk of being deciphered by the appearance of a huge amount of calculation and a decryption algorithm. Under such circumstances, the quantum key distribution system (QKD) is attracting attention as an encryption key distribution technique that is “never eavesdropped”.

  In QKD, a photon is generally used as a communication medium, and information is transmitted in quantum states such as polarization and phase. An eavesdropper on the transmission path steals information by tapping a photon being transmitted, etc., but it is not possible to completely return a photon that has been observed once to the quantum state before the observation due to the uncertainty principle of Heisenberg. This makes it possible to change the statistical value of received data detected by legitimate recipients. By detecting this change, the receiver can detect an eavesdropper on the transmission path.

  In the case of quantum key distribution using the phase of a photon, an optical interferometer is organized by a communication device on the transmission side and a communication device on the reception side (hereinafter referred to as “Alice” and “Bob”, respectively). Alice and Bob perform phase modulation at random. The output of 0 or 1 is obtained by the difference in the modulation phase depth, and then the same bit string is finally shared between Alice and Bob by collating part of the conditions when the output data is measured with Alice and Bob. be able to. Hereinafter, a general flow of quantum key generation will be briefly described with reference to FIG.

  In FIG. 1, random numbers generated on the Alice side are transmitted to Bob by quantum key distribution (single photon transmission), but most of the information amount is lost on the transmission path. At this stage, a random number sequence shared by Alice and Bob is called a raw key (raw key sharing S1). Subsequently, bits whose bases do not match are discarded by base collation between Alice and Bob (sequence S1.5), and the shared random number sequence halved by this is called a shift key (shift key sharing S2). .

  After this, it is assumed that the error correction process that corrects errors mixed in the quantum key distribution stage, the residual error detection process that finds errors that cannot be corrected after error correction, and the eavesdropper leak. Through privacy amplification that simplifies the amount of information to be obtained (sequence S2.5), the rest is the final key that is actually used as an encryption key (final key sharing S3). The final key generated in this way is used not only as an encryption key for encrypted communication, but also for message authentication for confirming that communication performed by the sender / receiver has not been tampered with.

  Here, if the key information input to the confidentiality enhancement process includes an error, the error is amplified by the confidentiality enhancement process. As disclosed in Non-Patent Document 1, when the confidentiality enhancement process is performed using a general m × n size Toeplitz matrix, the error rate is m / 2 times, as disclosed in Patent Document 1. When the secret enhancement method is used, the error rate is (n−m) m / 2n times. As disclosed in Non-Patent Document 2, taking into consideration the influence of statistical fluctuations when estimating the amount of leaked information, it is desirable to increase the matrix size n bits when performing the confidentiality enhancement process to 100 kbit or more. Therefore, even when any of the above-described secret enhancement methods is used, the error rate after the secret enhancement process is several tens of thousands times that before the process. Therefore, it is necessary to sufficiently reduce the error rate of the key information at the time of input to the confidentiality enhancement processing by error correction and residual error detection processing.

<Error correction and residual error detection processing>
As an error correction process, for example, there is a method as shown in Non-Patent Document 3. In this method, key information is divided into a plurality of blocks in Alice and Bob, a block including an error is specified by collating the parity of each block, and error correction is performed on the block by applying a Hamming code or the like. In addition, assuming that an even number of errors are included in one block, the secret bit string is rearranged at random, and parity verification and error correction are performed again.

  FIG. 2 shows an example of residual error detection processing when the number of parity calculations V = 4. In the residual error detection process, about half of the bits of the key information are selected at random, and the parity is verified between Alice and Bob. If the parity does not match, the error correction process is re-executed. If the parity check is repeated four times as shown in FIG. 2, the error rate of the shared key becomes 1/24 or less. However, since the encryption key information is leaked by performing the parity check, it is necessary to discard (V) bits for the number of times of the parity check. In the example of FIG. 2, since the parity check is repeated V = 4 times for the 24-bit key information, the 4-bit key is discarded and the 20-bit key information remains. Therefore, if the number of parity checks is increased in order to ensure a low error rate, the number of discarded bits increases, and the final key generation speed is degraded.

<Last key>
Returning to FIG. 1, the encryption key shared by the above-mentioned QKD is used for various purposes. The most typical use is encryption and decryption of common encryption communication (encryption communication S4). Among them, there is a method of using a one-time pad (One-Time-Pad) in which an encryption key is disposed only once, and a method of periodically updating an AES (Advanced Encryption Standard) encryption key.

  Furthermore, the communication (S1.5, S2.5) performed by Alice and Bob in the process of sharing the encryption key with QKD makes it impossible to ensure the security of the encryption key if its contents are tampered with. Although it is necessary to perform this, an encryption key is also used for this message authentication (message authentication S5).

  The authentication method disclosed in Non-Patent Document 4 is a method that can ensure information-theoretic safety, and an example of use is shown in FIG. In FIG. 3, the hash value is calculated by sequentially shortening the message by a matrix operation using an encryption key. If the hash values calculated by Alice and Bob are different, it is determined that there is a possibility that the communication content has been tampered with, and the encryption key corresponding to the communication content targeted when calculating the corresponding hash value is discarded.

JP 2007-086170 A

A. Tanaka, W. Maeda, S. Takahashi, A. Tajima, and A. Tomita, “Ensuring Quality of Shared Key through Quantum Key Distribution for Practical Application,” IEEE J. of Sel. Top. Quant. Elec., Vol. 15, no. 6, pp. 1622-1629 (2009). J. Hasegawa, M. Hayashi, T. Hiroshima, A. Tanaka, and A. Tomita, “Experimental Decoy State Quantum Key Distribution with Unconditional Security Incorporating Finite Statistics,” eprint arXiv: 0705.3081 (2007). “Secret-key Reconciliation by Public Discussion” G. Brassard and L. Salvail, in Advances in Cryptology-EUROCRYPT’93 Proceedings, Lecture Notes in Computer Science, Vol.765, p410-423 M. N. Wegman and J. L. Carter, “New Hash Functions and Their Use in Authentication and Set Equality,” J. Comput. System Sci. 22, 265 (1981).

As described above, the shared encryption key has various uses, and the required error rate may vary depending on the use. In other words, when used for One-Time-Pad, since the error rate of the final encryption key ≒ the error rate of encryption communication, if an error correction code is implemented in the encryption communication system, the error rate of the final encryption key Is acceptable even if it is relatively high. For example, an error correction code in which a BCH (3860, 3824) code and a BCH (2040, 1930) code are concatenated can correct an error rate of 3.3 × 10 ⁻³ to 1.0 × 10 ⁻¹² or less. The maximum error rate of the encryption key is allowed up to about 3.3 × 10 ⁻³ . On the other hand, when an encryption key is used for authentication purposes, if there is an error in even one bit in the encryption key, the hash value will be significantly different, and the encryption key corresponding to the target message at the time of hash value calculation will be discarded, generating the encryption key Because the speed is degraded, a sufficiently low error rate is required.

A specific example is given using FIG. Assuming that s = 128 bits and N = 32, the message bit a targeted for one hash value calculation is 512 Gbits, and the encryption key required for the hash value calculation is 16 kbits. When an authentication error is allowed once in 1000 times, the error rate of the encryption key needs to be 6.1 × 10 ⁻⁸ or less. In any of the above cases, since the error of the encryption key is increased by the confidentiality enhancement process, the encryption key error rate at the time of the confidentiality enhancement input is required to be a lower value. However, the ratio of error rates required in both cases is constant, and the latter example requires an error rate lower by about 1.8 × 10 ⁻⁵ , and is smaller in error correction processing and residual error detection processing. Only the encryption key can be obtained.

  Therefore, if error correction processing and residual error detection processing are performed based on the message authentication application, the final encryption key can be used for One-Time-Pad. It is an excessive specification for Pad use, and the encryption key generation speed is set low.

  Therefore, an object of the present invention is to provide a communication device and an encryption key generation method in an encryption key sharing system that can efficiently generate encryption keys that require different error rates.

  The communication apparatus according to the present invention is a communication apparatus that communicates with another communication apparatus through a transmission path, and includes an encryption key sharing unit that shares a first encryption key with the other communication apparatus, and the first encryption An error rate control unit that generates a second encryption key having an error rate according to the use of the encryption key from the key, and a storage unit that stores a plurality of second encryption keys having different error rates. .

  An encryption key generation method according to the present invention is an encryption key generation method in a communication device that communicates with another communication device through a transmission path, wherein an encryption key sharing unit obtains a first encryption key with the other communication device. The error rate control means generates a second encryption key having an error rate according to the use of the encryption key from the first encryption key, and the storage means stores a plurality of second encryption keys having different error rates, respectively. It is characterized by that.

  An encryption key sharing system according to the present invention is a system in which an encryption key is shared by communication between a first communication device and a second communication device through a transmission path, and the first communication device, the second communication device, Each of the first communication device and the second communication device generates a second encryption key having an error rate according to the use of the encryption key from the first encryption key, A plurality of second encryption keys having different error rates are respectively stored.

  According to the present invention, it is possible to efficiently generate an encryption key that requires different error rates.

FIG. 1 is a flowchart showing an encryption key generation procedure in general quantum encryption key distribution. FIG. 2 shows an example of residual error detection processing. FIG. 3 is a schematic diagram showing an example of hash value calculation used for message authentication. FIG. 4 is a block diagram showing a functional configuration of the communication device in the encryption key sharing system according to the first embodiment of the present invention. FIG. 5 is a block diagram showing a functional configuration of a communication apparatus in the encryption key sharing system according to the second embodiment of the present invention. FIG. 6 is a diagram illustrating an example of a management table referred to when the encryption key management unit according to the second embodiment designates the number of parity checks for residual error detection processing. FIG. 7 is a block diagram showing a functional configuration of the communication device in the encryption key sharing system according to the third embodiment of the present invention.

  According to the embodiment of the present invention, it is possible to generate and store encryption keys having different error rates by controlling the error correction circuit and / or the residual error detection circuit. Can be used for Hereinafter, embodiments of the present invention will be described in detail.

1. First Embodiment In the encryption key sharing system according to the first embodiment of the present invention, the use of the encryption key is set to One-Time-Pad encryption communication and message authentication, and a plurality of error correction circuits having different coding rates are used. Controls the error rate of the final encryption key.

1.1) Configuration As shown in FIG. 4, the transmission side communication device 11 (hereinafter referred to as Alice 11) and the reception side communication device 12 (hereinafter referred to as Bob 12) are connected via a transmission line. Thus, photon transmission from Alice 11 to Bob 12 and communication in the encryption key generation process between Alice 11 and Bob 12 are performed. The transmission path is made of an optical fiber, and includes a weak optical channel that performs photon transmission and a normal optical channel that performs communication in the encryption key generation process.

  Alice 11 includes a photon transmission unit 1101 that transmits a photon signal to Bob 12, a random number generation unit 1102, and a base collation unit 1103 that performs base collation by communicating with Bob 12. As already described, The verification unit 1103 obtains a shift key. The random number sequence rearrangement unit 1104 communicates with Bob 12 and rearranges the random number sequence of the shift key at random. The encryption key management unit 1115 distributes the rearranged shift keys to one of two paths for generating encryption keys having different error rates according to the control signal. Here, an encryption key with a relatively high error rate is obtained by the process of the path starting from the error correction unit 1105, and an encryption key with a relatively low error rate is obtained by the process of the path starting from the error correction unit 1106. Error correction units 1105 and 1106 correct errors existing in the shift key at different coding rates, and residual error detection units 1107 and 1108 detect errors remaining in the error-corrected key. The secrecy enhancing units 1109 and 1110 reduce key information that may be leaked to an eavesdropper, and a final encryption key generated in this way with a relatively high error rate and a final encryption key with a relatively low error rate Are stored in the final key storage unit 1111 and the final key storage unit 1112, respectively. When performing all the above-described communications, the hash calculation unit 1113 calculates a hash value from the communication content using an encryption key with a relatively low error rate stored in the final key storage unit 1112 and performs message authentication. . The encryption communication unit 1114 performs encryption and decryption for encryption communication using an encryption key with a relatively high error rate stored in the final key storage unit 1111.

  Bob 12 includes a photon receiving unit 1201 that receives a photon signal transmitted from Alice 11 and a base collation unit 1202 that performs base collation by communicating with Bob 12, and as described above, the base collation unit 1202 To obtain the shift key. The random number sequence rearrangement unit 1203 communicates with Alice 11 and rearranges the random number sequence of the shift key at random. The encryption key management unit 1214 distributes the rearranged shift keys to two paths. Here, an encryption key having a relatively high error rate is obtained by the process of the path starting from the error correction unit 1205, and an encryption key having a relatively low error rate is obtained by the process of the path starting from the error correction unit 1204. Error correction sections 1204 and 1205 correct errors existing in the shift key, and residual error detection sections 1206 and 1207 detect errors remaining in the error-corrected key. The secrecy enhancement units 1208 and 1209 reduce key information that may be leaked to an eavesdropper, and a final encryption key generated in this way with a relatively high error rate and a final encryption key with a relatively low error rate Are stored in the final key storage unit 1212 and the final key storage unit 1211, respectively. When performing all the above-described communications, the hash calculation unit 1210 calculates a hash value from the communication content using an encryption key with a relatively low error rate stored in the final key storage unit 1211 and performs message authentication. . The encryption communication unit 1213 performs encryption and decryption for encryption communication using an encryption key with a relatively high error rate stored in the final key storage unit 1212.

  Note that the random number generation unit 1102, the base collation unit 1103, the random number sequence rearrangement unit 1104, the error correction units 1105 and 1106, the residual error detection units 1107 and 1108, the privacy enhancement units 1109 and 1110, and the encryption key management unit 1115 in Alice 11 An equivalent function can be realized by executing a program stored in a memory (not shown) on a program control processor such as a CPU (Central Processing Unit) of Alice11.

  Similarly, the base collation unit 1202, the random number sequence rearrangement unit 1203, the error correction units 1204 and 1205, the residual error detection units 1206 and 1207, the confidentiality enhancement units 1208 and 1209, and the encryption key management unit 1214 in Bob12 are the CPUs of Bob12. An equivalent function can also be realized by executing a program stored in a memory (not shown) on a program control processor such as (Central Processing Unit).

1.2) Operation In Alice 11, the photon transmission unit 1101 transmits a photon signal to Bob 12 based on the output random number of the random number generation unit 1102. In Bob 12, the photon signal transmitted from the photon transmitter 1101 is received by the photon receiver 1201. Subsequently, the following processes are executed in Alice 11 and Bob 12, respectively.

  The base collating units 1103 and 1202 check only the bases selected at the time of transmission / reception and take out only the key bits whose selected bases match to obtain the shift keys. Next, the random number sequence rearranging units 1104 and 1203 rearrange the respective shift keys based on separately shared random numbers. The rearranged shift key is sent to the first path of the error correction units 1105 and 1205 set at a high coding rate by the encryption key management units 1115 and 1214, or the error correction unit 1106 set at a low coding rate. And 1204 to the second route.

  The first route is a route for generating an encryption key used for One-Time-Pad encryption communication, and an error correction unit 1105 or 1205 having a relatively high coding rate corrects an error in the shift key. That is, in the error correction unit 1105 of Alice 11 and the error correction unit 1205 of Bob 12, each shift key is divided into a plurality of blocks, and the blocks containing errors are identified by collating the parity of each block with each other. Error correction is performed by applying a code with a high coding rate. In the error-corrected shift key, residual error detection sections 1107 and 1207 detect errors remaining after error correction. If the parity does not match (if residual errors are detected), error correction sections 1105 and 1205 Each error correction is re-executed. Thus, the error-corrected shift key is input, and the concealment enhancing units 1109 and 1209 reduce key information that may have been leaked during photon transmission and store the final key in the final key storage units 1111 and 1212, respectively. The final key thus obtained is used as an encryption key in the encryption communication units 1114 and 1213.

  The second path is a path for generating an encryption key used for calculating a hash value for message authentication, and an error correction unit 1106 and 1204 having a relatively low coding rate corrects an error in the shift key. That is, in the error correction unit 1106 of Alice 11 and the error correction unit 1204 of Bob 12, each shift key is divided into a plurality of blocks, and the blocks containing errors are identified by collating the parity of each block with each other. Error correction is performed by applying a code with a low coding rate. In the error-corrected shift key, residual error detection sections 1108 and 1206 detect errors remaining after error correction, and if the parity does not match (if residual errors are detected), error correction sections 1106 and 1204 Each error correction is re-executed. Thus, the error-corrected shift key is input, and the concealment enhancing units 1110 and 1208 reduce key information that may have been leaked during photon transmission and store the final key in the final key storage units 1112 and 1211, respectively. Using the final key thus obtained, the hash calculators 1113 and 1210 calculate a hash value and perform message authentication.

  For example, when the error rate when performing photon transmission between the photon transmission unit 1101 and the photon reception unit 1201 is 3%, the error correction units 1105 and 1205 have a coding rate of 0.8 that can correct the error of 3%. LDPC (Low-Density Parity-check Code) codes are used, and error correction sections 1106 and 1204 use LDPC codes with a coding rate of 0.75 in order to sufficiently reduce the error rate after error correction. In this case, the error correction units 1105 and 1205 can increase the encryption key generation speed, but an encryption key having a relatively high error rate is generated due to an error that has not been corrected or corrected. On the other hand, since the error correction units 1106 and 1204 perform error correction with a sufficient margin, the error rate after error correction can be sufficiently reduced, but the coding rate is kept low, so that the encryption key generation speed is reduced. Becomes lower.

1.3) Effect As described above, according to the present embodiment, the error correction unit having a plurality of coding rates is provided by setting the error correction processing parameters according to the error rate required for the encryption key. The amount of key bits discarded in vain can be reduced, and an encryption key corresponding to the application can be efficiently generated.

  As the final encryption key, one-time-pad encryption communication allows a relatively high error rate to improve encryption key generation speed, and message authentication uses at the expense of encryption key generation speed. Although a sufficiently low error rate is ensured, the present invention is not limited to this. When the encryption key is used for the purpose of periodically updating the encryption key for AES encryption communication, the error correction processing parameters may be changed according to the update frequency of the encryption key.

  Further, the method for controlling the error rate of the encryption key is not limited to changing the coding rate of the error correction process, and the number of parity checks performed in the residual error detection process may be changed as will be described later. Furthermore, although the quantum key distribution method is used as means for securely sharing an encryption key including an error between Alice 11 and Bob 12, other secret key sharing means may be used.

2. Second Embodiment In the second embodiment of the present invention, the generated encryption key is used for One-Time-Pad encryption communication and message authentication, and by changing the parameters of one residual error detection circuit, the final encryption key is changed. A method for controlling the error rate will be described.

2.1) Configuration As shown in FIG. 5, a transmission side communication device 21 (hereinafter referred to as Alice 21) and a reception side communication device 22 (hereinafter referred to as Bob 22) are connected via a transmission line, and will be described below. Thus, photon transmission from Alice 21 to Bob 22 and communication in the encryption key generation process between Alice 21 and Bob 22 are performed.

  Alice 21 includes a photon transmitter 2101 that transmits a photon signal to Bob 22, a random number generator 2102, and a base collator 2103 that performs base collation by communicating with Bob 22, as already described. The base verification unit 2103 obtains the shift key. The random number sequence rearrangement unit 2104 communicates with Bob 22 to randomly rearrange the random number sequence of the shift key, and the error correction unit 2105 corrects an error existing in the rearranged shift key.

  The encryption key management unit 2112 outputs the shift key after error correction to the subsequent residual error detection unit 2106 and sets the number of parity checks performed in the residual error detection unit 2106 with reference to the management table 2112a according to the control signal. . The management table 2112a is stored in a memory (not shown). The residual error detection unit 2106 detects an error remaining in the error-corrected key by the set number of parity checks. The secrecy enhancement unit 2107 reduces key information that may be leaked to an eavesdropper, and according to the control signal, the number of parity checks is small (the error rate is relatively high) and the number of parity checks is large ( The final encryption key having a relatively low error rate is stored in the final key storage unit 2108 and the final key storage unit 2109, respectively. When performing all the above-described communications, the hash calculation unit 2110 calculates a hash value from the communication content using an encryption key with a relatively low error rate stored in the final key storage unit 2108, and performs message authentication. . The encryption communication unit 2111 performs encryption and decryption for encryption communication using an encryption key with a relatively high error rate stored in the final key storage unit 2108.

  Bob 22 includes a photon receiving unit 2201 that receives a photon signal transmitted from Alice 21 and a base collation unit 2202 that performs base collation by communicating with Bob 22, and as described above, base collation A shift key is obtained by the unit 2202. The random number sequence rearrangement unit 2203 communicates with Alice 21 to rearrange the random number sequence of the shift key at random, and the error correction unit 2204 corrects an error existing in the rearranged shift key.

  The encryption key management unit 2211 outputs the error-corrected shift key to the subsequent residual error detection unit 2205 and sets the number of parity checks performed in the residual error detection unit 2205 with reference to the management table 2211a according to the control signal. . The management table 2211a is stored in a memory (not shown). The residual error detection unit 2205 detects an error remaining in the error-corrected key by the set number of parity checks. The secrecy enhancing unit 2206 reduces key information that may be leaked to an eavesdropper, and according to the control signal, the number of parity checks is small (the error rate is relatively high) and the number of parity checks is large ( The final encryption key (with a relatively low error rate) is stored in the final key storage unit 2209 and the final key storage unit 2208, respectively. When performing all the above-described communications, the hash calculation unit 2207 calculates a hash value from the communication content using an encryption key with a relatively low error rate stored in the final key storage unit 2208, and performs message authentication. . The encryption communication unit 2210 performs encryption and decryption for encryption communication using an encryption key with a relatively high error rate stored in the final key storage unit 2209.

  As shown in FIG. 6, in the management table 2112a of Alice 21 and the management table 2211a of Bob 22, the number of parity checks is set for each key ID whose use is determined. Here, the parity check is repeated 32 times for the encryption communication key, but the error rate is lowered by 1024 times for the authentication key. Note that the number of parity checks may be determined according to the use of the encryption key, and the number is not limited.

2.2) Operation In Alice 21, the photon transmission unit 2101 transmits a photon signal to Bob 22 based on the output random number of the random number generation unit 2102. In Bob 22, the photon reception unit 2201 receives the photon signal transmitted from the photon transmission unit 2101. Subsequently, the base collation units 2103 and 2202 collate the bases selected at the time of transmission / reception, extract only the key bits that match the selected bases, and obtain the shift key. Next, the random number sequence rearranging units 2104 and 2203 rearrange the respective shift keys based on separately shared random numbers.

  Error correction sections 2105 and 2204 correct errors in the rearranged shift keys. That is, the error correction unit 2105 of Alice 21 and the error correction unit 2204 of Bob 22 identify each block containing an error by dividing each shift key into a plurality of blocks and collating the parity of each block with each other. Perform error correction on. In the error key thus corrected, the residual error detection units 2106 and 2205 detect errors remaining after error correction for the number of parity checks set by the encryption key management units 2112 and 2211, and if the parity does not match ( If a residual error is detected), error correction is performed again in error correction units 2105 and 2204, respectively.

  In this way, the error-corrected shift key is input, and the concealment enhancing units 2107 and 2206 reduce key information that may have been leaked during photon transmission, and the final key obtained with a small number of parity checks according to the control signal. The final keys obtained by a large number of parity checks are stored in the final key storage units 2108 and 2209, respectively, in the final key storage units 2109 and 2208. Thus, the final key having a relatively high error rate stored in the final key storage units 2108 and 2209 is used as an encryption key in the cryptographic communication units 2111 and 2210, and the relative error stored in the final key storage units 2109 and 2208 is used. The hash calculators 2110 and 2207 calculate the hash value using the final key with a low rate, and perform message authentication.

  In this embodiment, the encryption key is managed by ID, and the encryption key management units 2112 and 2211 change the number of parity checks in the residual error detection processing based on the management tables 2112a and 2211a as shown in FIG. Encryption keys having different error rates can be generated depending on the circuit. The encryption key set with a high error rate by reducing the number of parity checks is stored in the final key storage units 2108 and 2209 and is used by the encryption communication units 2111 and 2210 for One-Time-Pad encryption communication. Also, an encryption key with a low error rate set by increasing the number of parity checks is stored in the final key storage units 2109 and 2208 for use in message authentication, and is used when the hash calculation units 2110 and 2207 calculate hash values.

2.3) Effects Also in this embodiment, the same effects as in the first embodiment can be obtained. Furthermore, in this embodiment, since the error rate of the final encryption key is controlled by managing the encryption key with the ID and changing the number of parity checks using the same circuit, there is an advantage that the number of implementation circuits can be reduced. . Further, since the encryption key management units 2112 and 2211 can generate final keys having a plurality of error rates based on the management tables 2112a and 2211a, there is an advantage that encryption keys for a wide range of applications can be easily generated.

  In addition, this embodiment and 1st Embodiment can also be combined. That is, the error correction units 2105 and 2204 and the subsequent parts in FIG. 5 can be divided into two paths in the same manner as in the first embodiment, and this embodiment can be applied to each.

3. Third Embodiment In the third embodiment of the present invention, the generated encryption key is used for a plurality of encryption communications that require different encryption key error rates. The error rate control method is the same as that in the second embodiment.

3.1) Configuration As shown in FIG. 7, a transmission side communication device 31 (hereinafter referred to as Alice 31) and a reception side communication device 32 (hereinafter referred to as Bob 32) are connected via a transmission line. Thus, photon transmission from Alice 31 to Bob 32 and communication in the encryption key generation process between Alice 31 and Bob 32 are performed.

  Alice 31 includes a photon transmission unit 3101 that transmits a photon signal to Bob 32, a random number generation unit 3102, and a base collation unit 3103 that performs base collation by communicating with Bob 32. As already described, The verification unit 3103 obtains a shift key. The random number sequence rearrangement unit 3104 communicates with Bob 32 to randomly rearrange the random number sequence of the shift key, and the error correction unit 3105 corrects an error existing in the rearranged shift key.

  The encryption key management unit 3112 outputs the shift key after error correction to the subsequent residual error detection unit 3106, and sets the number of parity checks performed in the residual error detection unit 3106 with reference to the management table 3112a according to the control signal. . The management table 3112a is stored in a memory (not shown). The residual error detection unit 3106 detects an error remaining in the error-corrected key by the set number of parity checks. The secrecy enhancing unit 3107 reduces key information that may be leaked to an eavesdropper, and according to the control signal, the number of parity checks is small (the error rate is relatively high) and the number of parity checks is large ( The final encryption key having a relatively low error rate is stored in the final key storage unit 3108 and the final key storage unit 3109, respectively. The final key stored in the final key storage unit 3108 is used by the encryption communication unit 3111 for One-Time-Pad encryption communication, and the final key stored in the final key storage unit 3109 is AES encrypted by the encryption communication unit 3111. Used for communication key update.

  Bob 32 includes a photon receiving unit 3201 that receives a photon signal transmitted from Alice 31, and a base collation unit 3202 that communicates with Bob 32 to perform base collation. As described above, the base collation unit 3202 To obtain the shift key. The random number sequence rearrangement unit 3203 communicates with Alice 31 to randomly rearrange the random number sequence of the shift key, and the error correction unit 3204 corrects an error existing in the rearranged shift key.

  The encryption key management unit 3211 outputs the shift key after error correction to the subsequent residual error detection unit 3205 and sets the number of parity checks performed in the residual error detection unit 3205 with reference to the management table 3211a according to the control signal. . The management table 3211a is stored in a memory (not shown). The residual error detection unit 3205 detects errors remaining in the error-corrected key by the set number of parity checks. The secrecy enhancement unit 3206 reduces key information that may be leaked to an eavesdropper, and the number of parity checks is small (the error rate is relatively high) and the number of parity checks is large according to the control signal ( The final encryption key having a relatively low error rate is stored in the final key storage unit 3209 and the final key storage unit 3208, respectively. When performing all the above-described communications, the hash calculation unit 3207 calculates a hash value from the communication content using an encryption key with a relatively low error rate stored in the final key storage unit 3208, and performs message authentication. . The encryption communication unit 3210 performs encryption and decryption for encryption communication using an encryption key with a relatively high error rate stored in the final key storage unit 3209.

  In the management table 3112a of Alice 31 and the management table 3211a of Bob 32, the number of parity checks is set for each key ID for which the usage shown in FIG. 6 is determined, as in the second embodiment.

3.2) Operation In Alice 31, the photon transmitter 3101 transmits a photon signal to Bob 32 based on the output random number of the random number generator 3102. In Bob 32, the photon reception unit 3201 receives the photon signal transmitted from the photon transmission unit 3101. Subsequently, the base collating units 3103 and 3202 collate the bases selected at the time of transmission / reception and take out only the key bits whose selected bases match to obtain a shift key. Next, the random number sequence rearranging units 3104 and 3203 rearrange the respective shift keys based on separately shared random numbers.

  Error correction sections 3105 and 3204 correct errors in the rearranged shift keys. That is, the error correction unit 3105 of Alice 31 and the error correction unit 3204 of Bob 32 divide each shift key into a plurality of blocks, identify blocks including errors by collating the parity of each block with each other, and Perform error correction on. In the error key thus corrected, the residual error detection units 3106 and 3205 detect errors remaining after error correction by the number of parity checks set by the encryption key management units 3112 and 3211, and if the parity does not match ( If a residual error is detected), error correction is performed again in error correction sections 3105 and 3204, respectively.

  In this way, the error-corrected shift key is input, and the concealment enhancing units 3107 and 3206 reduce key information that may have been leaked during photon transmission, and the final key obtained with a small number of parity checks according to the control signal. The final keys obtained by a large number of parity checks are stored in the final key storage units 3108 and 3209 in the final key storage units 3109 and 3207, respectively. Thus, the final key having a relatively high error rate stored in the final key storage units 3108 and 3209 is used in the cryptographic communication units 3111 and 3210 for One-Time-Pad encryption communication and stored in the final key storage units 3109 and 3208. The final key having a relatively low error rate is used in the cryptographic communication units 3110 and 3207 to update the key for AES cryptographic communication.

3.3) Effects Also in this embodiment, the same effects as in the second embodiment can be obtained. In this embodiment, One-Time-Pad and AES are exemplified as the encryption communication method, but the encryption communication method is not limited to this. Any application with different required encryption key error rates may be used.

4). Additional Notes Part or all of the above-described embodiments may be described as the following additional notes, but are not limited thereto.

(Appendix 1)
A communication device that communicates with other communication devices through a transmission path,
Encryption key sharing means for sharing a first encryption key with the other communication device;
An error rate control means for generating a second encryption key having an error rate according to the use of the encryption key from the first encryption key;
Storage means for storing each of a plurality of second encryption keys having different error rates;
A communication apparatus comprising:

(Appendix 2)
The error rate control means includes error correction means for correcting an error included in the first encryption key, and residual error detection means for detecting an error that could not be corrected by the error correction,
2. The error rate is controlled by changing an encoding rate of an error correction code used in the error correction unit and / or a parity check number applied to the residual error detection unit. Communication device.

(Appendix 3)
The communication apparatus according to appendix 2, wherein the error rate control means has a management table in which a plurality of parity check times are predetermined according to the use of the encryption key.

(Appendix 4)
The error rate control means includes a plurality of error correction means having different coding rates, and controls the error rate by selecting one of the plurality of error correction means according to the use of the encryption key. 4. The communication device according to appendix 2 or 3, which is characterized.

(Appendix 5)
An encryption key generation method in a communication device that communicates with another communication device through a transmission path,
An encryption key sharing means shares a first encryption key with the other communication device;
An error rate control means generates a second encryption key having an error rate according to the use of the encryption key from the first encryption key;
The storage means stores a plurality of second encryption keys having different error rates,
An encryption key generation method characterized by the above.

(Appendix 6)
The error rate control means corrects an error included in the first encryption key, detects a residual error that could not be corrected by the error correction, and an encoding rate of an error correction code used for the error correction and Controlling the error rate by changing the number of parity checks applied to the residual error detection;
The encryption key generation method according to appendix 5, characterized in that:

(Appendix 7)
The encryption key generation method according to appendix 6, wherein the error rate control means has a management table in which a plurality of parity check times are predetermined according to the use of the encryption key.

(Appendix 8)
The error rate control means includes a plurality of error correction means having different coding rates, and controls the error rate by selecting one of the plurality of error correction means according to the use of the encryption key. The encryption key generation method according to appendix 6 or 7, which is characterized by the following.

(Appendix 9)
A system in which an encryption key is shared by communication between a first communication device and a second communication device through a transmission path,
Sharing a first encryption key between the first communication device and the second communication device;
Each of the first communication device and the second communication device generates a second encryption key having an error rate corresponding to the use of the encryption key from the first encryption key, and a plurality of second encryption keys having different error rates are generated. Accumulate each,
An encryption key sharing system characterized by that.

(Appendix 10)
Each of the first communication device and the second communication device corrects an error included in the first encryption key, detects a residual error that could not be corrected by the error correction, and is used for the error correction The encryption key sharing system according to appendix 9, wherein the error rate is controlled by changing a coding rate of an error correction code and / or a number of parity checks applied to the residual error detection.

(Appendix 11)
The encryption key sharing system according to appendix 10, wherein each of the first communication device and the second communication device has a management table in which a plurality of parity check counts are predetermined according to the use of the encryption key. .

(Appendix 12)
Each of the first communication device and the second communication device is provided with a plurality of error correction units having different coding rates, and selecting one of the plurality of error correction units according to the use of the encryption key 12. The encryption key sharing system according to appendix 10 or 11, wherein the error rate is controlled.

(Appendix 13)
A program for functioning a program control processor in a communication device that communicates with another communication device through a transmission line,
An encryption key sharing means shares a first encryption key with the other communication device;
An error rate control means generates a second encryption key having an error rate according to the use of the encryption key from the first encryption key;
The storage means stores a plurality of second encryption keys having different error rates,
A program for causing the program control processor to function as described above.

(Appendix 14)
The error rate control means corrects an error included in the first encryption key, detects a residual error that could not be corrected by the error correction, and an encoding rate of an error correction code used for the error correction and Controlling the error rate by changing the number of parity checks applied to the residual error detection;
The program according to appendix 13, characterized by:

(Appendix 15)
15. The program according to appendix 14, wherein the error rate control means has a management table in which a plurality of parity check times are predetermined according to the use of the encryption key.

(Appendix 16)
The error rate control means includes a plurality of error correction means having different coding rates, and controls the error rate by selecting one of the plurality of error correction means according to the use of the encryption key. The program according to appendix 14 or 15, which is characterized.

  The present invention can be used for highly confidential communication using a common encryption key distribution technique represented by a quantum encryption key distribution technique. The quantum encryption key distribution method may be either a unidirectional type or a round-trip type.

11, 21, 31 Alice (transmission side communication device)
1101, 2101, 3101 Photon transmitter 1102, 2102, 3102 Random number generator 1103, 2103, 3103 Base collator 1104, 2104, 3104 Random number rearranger 1105, 1106, 2105, 3105 Error corrector 1115, 2112, 3112 Encryption Key management units 1107, 1108, 2106, 3106 Residual error detection units 1109, 1110, 2107, 3107 Concealment enhancement units 1111, 1112, 2108, 2109, 3108, 3109 Final key accumulation units 1113, 2110 Hash calculation units 1114, 2111, 3110 , 3111 Cryptographic communication unit 12, 22, 32 Bob (receiving side communication device)
1202, 2202, 3202 Base collation unit 1203, 2203, 3203 Random number sequence rearrangement unit 1204, 1205, 22045, 3204 Error correction unit 1214, 2211, 3211 Encryption key management unit 1206, 1207, 2205, 3205 Residual error detection unit 1208, 1209, 2206, 3206 Concealment enhancing unit 1211, 1212, 2208, 2209, 3208, 3209 Final key storage unit 1210, 2207 Hash calculation unit 1213, 2210, 3207, 3210 Cryptographic communication unit

Claims (10)

A communication device that communicates with other communication devices through a transmission path,
Encryption key sharing means for sharing a first encryption key with the other communication device;
An error rate control means for generating a second encryption key having an error rate according to the use of the encryption key from the first encryption key;
Storage means for storing each of a plurality of second encryption keys having different error rates;
A communication apparatus comprising: The error rate control means includes error correction means for correcting an error included in the first encryption key, and residual error detection means for detecting an error that could not be corrected by the error correction,
2. The error rate is controlled by changing an encoding rate of an error correction code used in the error correction unit and / or a parity check number applied to the residual error detection unit. Communication equipment.   The communication apparatus according to claim 2, wherein the error rate control unit has a management table in which a plurality of parity check times are predetermined according to the use of the encryption key.   The error rate control means includes a plurality of error correction means having different coding rates, and controls the error rate by selecting one of the plurality of error correction means according to the use of the encryption key. The communication device according to claim 2 or 3, characterized in that An encryption key generation method in a communication device that communicates with another communication device through a transmission path,
An encryption key sharing means shares a first encryption key with the other communication device;
An error rate control means generates a second encryption key having an error rate according to the use of the encryption key from the first encryption key;
The storage means stores a plurality of second encryption keys having different error rates,
An encryption key generation method characterized by the above. The error rate control means corrects an error included in the first encryption key, detects a residual error that could not be corrected by the error correction, and an encoding rate of an error correction code used for the error correction and Controlling the error rate by changing the number of parity checks applied to the residual error detection;
The encryption key generation method according to claim 5.   7. The encryption key generation method according to claim 6, wherein the error rate control means has a management table in which a plurality of parity check times are predetermined according to the use of the encryption key.   The error rate control means includes a plurality of error correction means having different coding rates, and controls the error rate by selecting one of the plurality of error correction means according to the use of the encryption key. The encryption key generation method according to claim 6 or 7, characterized in that A system in which an encryption key is shared by communication between a first communication device and a second communication device through a transmission path,
Sharing a first encryption key between the first communication device and the second communication device;
Each of the first communication device and the second communication device generates a second encryption key having an error rate corresponding to the use of the encryption key from the first encryption key, and a plurality of second encryption keys having different error rates are generated. Accumulate each,
An encryption key sharing system characterized by that. A program for functioning a program control processor in a communication device that communicates with another communication device through a transmission line,
An encryption key sharing means shares a first encryption key with the other communication device;
An error rate control means generates a second encryption key having an error rate according to the use of the encryption key from the first encryption key;
The storage means stores a plurality of second encryption keys having different error rates,
A program for causing the program control processor to function as described above.

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